The effect of covertly manipulating the energy density of mixed diets on ad libitum food intake in ‘pseudo free-living’ humans

Abstract

OBJECTIVE: This study examined the effects of covert alterations in the energy density (ED) of mixed, medium fat (MF) diets on ad libitum food and energy intake (EI), subjective hunger and body weight in humans. DESIGN: Randomised cross-over design. Subjects were each studied three times (factorial design), during 14 d, throughout which they had ad libitum access to one of three covertly-manipulated MF diets. SUBJECTS: Six healthy men, mean age (s.e.m.) 30.0 y (12.76 y), mean weight 71.67 kg (19.80 kg); mean height 1.79 m (0.22 m), body mass index (BMI) 22.36 (2.60) kg/m 2 , were studied. The fat, carbohydrate (CHO) and protein in each diet (as a proportion of the total energy) and energy density (ED) were, low-ED (LED), 38:49:13%; 373 kJ/100 g; medium-ED (MED), 40:47:13%; 549 kJ/100 g; high-ED (HED), 39:48:13%; 737 kJ/100 g. Subjects could alter the amount but not the composition of foods eaten. They were resident in (but not con®ned to) a metabolic suite throughout the study. RESULTS: Solid food intake decreased as ED increased, giving mean values of 2.84, 2.51 and 2.31 kg/d, respectively. This was insuf®cient to defend energy balance, since energy intake increased with increasing ED (F (2,10) 16.08; P`0.001) giving mean intakes of 10.12, 12.80 and 16.17 MJ/d, respectively. Rated pleasantness of food (measured on visual analogue scales) was not signi®cantly different between diets nor was subjective hunger different between the LED, MED and HED diets, respectively. Diet signi®cantly affected body weight (F (2,10) 4.62; P 0.038), producing changes of 71.20, 0.02 and 0.95 kg, respectively, by day 14. CONCLUSION: Dietary ED can in¯uence EI and body weight, since changes in amount eaten alone are insuf®cient to defend energy balance, when subjects feed on unfamiliar diets and diet selection is precluded. Comparison with our previous studies suggest that there was compensation in solid food intake when ED was altered using mixed diets (as in this study) compared to previous studies which primarily used fat or CHO to alter dietary ED.

High-fibre, low-fat diet predicts long-term weight loss and decreased type 2 diabetes risk: the Finnish Diabetes Prevention Study

“…People have been shown to be only partly able to compensate for changes in dietary energy density by increasing or decreasing the total amount of food, at least in short-term clinical studies [44,45]. In our analysis, dietary energy density was highly significantly associated with sustained weight reduction; on the other hand, energy density is a composite factor of dietary fat, fibre and water.…”

Dietary energy density increases during early childhood irrespective of familial predisposition to obesity: results from a prospective cohort study

“…With respect to the current investigation, however, it should be noted that the sample size (n ¼ 49 children) might have been too small to detect significant associations between the two variables. Although laboratory and clinical studies that were conducted in adults showed a positive-association between dietary ED and weight gain, [33][34][35] data from cross-sectional epidemiological studies showed inconsistent results. 36 For example, a recent cross-sectional study in adults showed that normal-weight individuals had diets with a lower ED than did obese individuals.…”

High and low carbohydrate and fat intakes: limits imposed by appetite and palatability and their implications for energy balance

“…There are a number of examples which show that fat exerts detectable albeit relatively modest effects on appetite and EB which are independent of its contribution to dietary ED. CHO appears to exert a more acute effect on satiety than fat (Cotton et al, 1994), and three other studies have found this relatively subtle effect to be independent of ED (Rolls et al, 1994;Johnstone et al, 1996;Stubbs et al, 1997a). In one of these studies, the low satiating ef®ciency of fat in the short term appeared to be related to its low osmotic load, as indicated by the subjective thirst of the subjects .…”

“…Physiological signals may affect FB either directly or through perceptible changes in functional integrity (for example, feeling weak and tired during energy restriction), which can act as learning cues for feeding. If this argument is correct, it may be that studies which have examined the impact of covert dietary manipulations on appetite and EB actually assess the extremes required for physiological signals to in¯uence compensatory changes in FB (Van Stratum et al, 1978;Lissner et al, 1987;Kendall et al, 1991;Cotton et al, 1994;Stubbs et al, 1995aStubbs et al, , b, 1996Stubbs et al, , 1997a.…”

“…Problems with obtaining accurate dietary intake measures (Black et al, 1991;Schoeller, 1990) and lack of knowledge of the relationship between¯uid and FI preclude conclusive statements. While the impact of altering dietary ED using differing nutrients, on EI and EB is beginning to emerge in laboratory studies lasting up to two weeks (Lissner et al, 1987;Kendall et al, 1991;Thomas et al, 1992;Stubbs et al, 1995aStubbs et al, , 1997aO'Reilly et al, 1997), the extent to which humans adapt FB to changes in the dietary ED over longer periods is unknown. The few longer-term interventions that have altered the nutrient density of certain foods have shown relatively good compensation over periods of a few months (Aaron et al, 1999;Gatenby et al, 1995;Zimmermans et al, undated).…”